Reject multiple k6 scenarios in script validation

[amarkdotdev]

Summary

• Enforce a single k6 scenario in browser and scripted check validation, matching triage guidance that SM only supports one VU/scenario.
• Return a clear user-facing error when options.scenarios defines more than one scenario, instead of validating only the first.
• Add unit coverage for multi-scenario rejection in browser and scripted validators.

Fixes #1741

Test plan

• yarn test src/schemas/forms/script/validation.test.ts
• In the check editor, paste a browser script with two scenarios and confirm the form shows the single-scenario error
• Confirm a valid single-scenario browser/scripted check still saves successfully

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[cursor]

Scenario count skips non-literal values

Medium Severity

countScenarios only counts entries whose values are inline ObjectExpressions. Scenario configs referenced by identifier (including shorthand like scenarios: { ui, api }) are ignored, so multi-scenario scripts can pass the new single-scenario check.

 

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[ckbedwell]

@amarkdotdev Thanks for your contribution and picking this up! Can you sign the CLA, please? 🙏